What happened with a sacrifice was both the giver would agree for a time with the priest at the temple, and then he would go and get a perfect animal. It depended on the god that they were sacrificing to but usually the gods which were in the heavens got white animals and the underworld and earth gods and goddesses got black. The animals had to be perfect. Then the person who was sacrificing the animal would decorate it with ribbons and flowers. For special festivals some would even guild the animal’s horns in gold!
They would then travel through the streets with flutes playing and incense burning. If the animal stumbled or didn’t go willingly (which was probably inevitable) then it was taken as a bad omen and they would have to start over with a new animal, if anything went wrong.
It took place on the altar, which was outside, so not to stain the glory of the temple inside with the gore. The priest would watch over the whole thing with his head covered by his toga so as not to let any evil in, and would wash his hands in sacred water before the ceremony started. The animal was sprinkled with wine and mola salsa (sacred bread baked by the Vestal Virgins). During that the priest would say with a prayer.
The animal was then stunned by a hammer then had its throat cut. The animal was then cut so that its guts could be taken out and examined by a...